Antibiotics of cephalosporin series are widely used in therapy for the treatment of diseases which are caused by general pathogenic bacteria in human beings and animals. It is known that such antibiotics are useful for the treatment of diseases caused by bacteria-exhibiting resistance to other antibiotics, e.g., penicillin-resistant bacteria; and also for the treatment of penicilin-sensitive patients.
It is also well known that the activity of a cephalosporin compound may be varied by manipulating the substituents on the 3- and/or 7-position of the cephem ring. In this regard, there have been many studies made in developing a variety of cephalosporin antibiotics with broad spectra of antibiotic activities by introducing a 7-.beta. acylamido group and various substituents on the 3-position of the cephem ring.
For example, certain cephalosporin compounds which have the following formula (A) substituted by 2-aminothiazolylacetamino group on the 7-position have been proposed as effective antibiotics against Gram-negative and Gram-positive bacteria: ##STR2##
Specifically, cephalosporin compounds of formula (A) having a quaternary aromatic ammonium salt on the 3-position are disclosed in U.S. Pat. No. 4,258,041(ceftazidime), Japanese Laid-Open Patent Publication 86007280(DQ-2556) and EP Application No. 64740(cefpirome). The above cephalosporins are known to exhibit good antibiotic activities against enterobacteria; however, they still suffer from unsatisfactory antibiotic activities against certain bacterial species. For example, ceftazidime has a relatively low activity against Staphylococcus, even though it has a higher activity against Pseudomonas, compared with DQ-2556. Further, cefpirome shows an improved activity against Gram-negative and Gram-positive bacteria, but its activity against Pseudomonas is inferior to ceftazidime.